Does cannabis cause psychosis?

PsyBlog has picked up on a recent article in The Independent that discusses the debate over cannabis and the risk of developing psychosis. This is currently topical in the UK in light of an expected government report about the legal re-classification of the drug.

Previously, it was known that there is an association between cannabis and psychosis, although it was not clear whether cannabis contributed to psychosis, or whether people with psychosis were simply more likely to ‘self-medicate’ with cannabis in an attempt to feel better.

A 2004 article in the British Journal of Psychiatry reviewed studies which allow a causal link, rather than simply an association, to be inferred, and sparked a debate (see PubMed entry) which has now led the goverment to think again about the recent downgrading of the legal penalties for possessing cannabis.

Although many psychiatrists and researchers now believe that cannabis is a causal factor in psychosis, the effect is still thought to be small in most people. Genetic studies have reported, however, that people holding certain versions of the COMT gene may be more likely to develop psychosis when cannabis is used.

Nevertheless, an alternative debate centres on whether public education and health services benefit for such a widely used drug to be outlawed, when other, potentially more harmful substances, are legally sold.

Link to Independent article ‘Cannabis: Can it really drive you mad?’Link to PubMed entry of 2004 debate in the BJP (link to free full text articles).

2 thoughts on “Does cannabis cause psychosis?”

What, no comments about the mother in the article who says she’d rather her kid do cocaine than play video games, because at least when you do cocaine you’re out and doing something? (She says video games are lazy.)